The present invention is related to the field of spread spectrum communications systems and more particularly to an improved spread spectrum demodulator utilizing matched filtering techniques.
Spread spectrum communication systems utilize a transmission bandwidth many times as large as the information bandwidth in order to achieve jam resistance. Additional advantages include multipath signal rejection and a low probability of detection. A spread spectrum transmitter generates a data modulated signal, which signal has its energy spread over a frequency band considerably wider than the data rate. Generally a PN sequence is used to modulate the phase of the carrier signal. Within the receiver there is usually provided a matched filter which filter is designated to have an impulse response which is the time-reverse of the transmitter's output waveform. The matched filter thus provides a match between the transmitted waveform and the receiver's response. Matched filters that utilize surface acoustic wave devices (SAW's) have been used in spread spectrum data transmission systems.
Two publications of interest for purposes of establishing the state of the art are "Surface Acoustic Wave Devices And Applications" by D. P. Morgan, Ultrasonics, May 1973, pages 121-128; and "Surface Acoustic Wave Devices And Applications (Spread Spectrum Processors)" by B. J. Hunsinger, Ultrasonics, November 1973, pages 254-263.